In olden times a dish of carrots, sea tangle ("Kombu") and soybeans cooked together in an iron pan had widely been eaten as a daily dish. Recently, however, the use of iron pots has become unpopular so that it is no longer a source of iron supply. In the preparation of soybean cake ("Miso") or soybean sauce ("Shoyu"), the starting soybeans are boiled in an iron pot and then combined with rice malt (Koji) to be processed to "Miso" or combined with parched wheat to make "Koji" to be processed to "Shoyu". The iron which is derived from an iron pot used in the course of preparing "Shoyu" or "Miso" reacts with lactic acid producing during the fermentation process and is converted to an organic form or and is introduced into the yeast cells. However, iron that remains in an organic form in fermented products causes deterioration in the color of the products with time. Therefore the fermentation equipment containing iron to produce the fermentation products is no longer used. Consequently, these fermentation products are no longer a source of iron supply. On the other hand, mixtures of ferric citrate or ferrous lactate with a plant extract have heretofore been used for supplying iron but occasionally have caused inflammation on or around the lips or anorexia.
We previously developed a process for preparing fermented food products of soybean by digesting boiled and powdered raw soybeans with a digestive enzyme and then fermenting the digest with yeast, in which a patent application was filed (Japanese Patent Publication No. 50816/81). According to the preparative process fermented food products of soybeans, which do not contain unpleasant color and odor caused by the growth of fungi and bacteria, are produced. Whereas soybeans are a nutritious food rich in protein, lipid and saccharide, its iron content is as low as 10 mg or below per 100 g of edible part. As a result of extensive studies for reinforcing the iron content in the above-mentioned fermented food products of soybeans, we have found that the iron enriched food products having good flavor and high nutritive value are obtained by digesting pulverized soybeans and cultivating yeast in the digest in the presence of an iron compound.
Also provided are iron enriched food products having good flavor and being rich in carotene by digesting pulverized carrots and cultivating yeast in the digest in the presence of an iron compound.
Furthermore, there are provided iron enriched food products having very high nutritive value and being rich in iron in readily absorbable form, by digesting pulverized soybeans and pulverized carrots and cultivating yeast in the digest mixture in the presence of an iron compound.